(Ph1). In this phase, optical phenomena are discussed in order to build a basic idea of
light as a massless entity travelling in space, which possess energy which guides the
description of processes in which light itself interacts with matter causing different
effects, such as heating, penetration, ionization and fluorescence. The difference
between Snell’s law for refraction and the phenomenology of light transmission
through a transparent medium is discussed with students in order to distinguish the
plan of formalized phenomenological description in macroscopic terms and the plan
according to which light–matter interaction processes are interpreted in terms of
energy. A reflection with students on the difference between refraction and transmission of light stimulates an analysis of the two point of view under which those
two apparently similar phenomena, are seen: refraction is a macroscopic phenomenological description of the light path across the interface between two mediums
with different indexes of refraction, while, when speaking of transmission processes,
the focus is put on the interaction between light and matter and implies a deeper
analysis, in particular on the energetic plan.
The problem of what “to see” means is posed to students, with the aim of identify,
from the discussion of spontaneous models, the role of the observer, of the observed
object and of the light (Ph2).
A fundamental parameter enters in the description of the vision mechanism: the
colour (Ph3). Radiation gains a significant role in this perspective and poses the
question of what the colour physically represents, starting from the observation that
what is seen depends on the type of light contextualizing in the case of different
picture or painting appear when illuminated by different lights. Surface absorption
and nano-structuring allows to understand the mechanism according to which
different objects appear differently coloured, in particular the colour of an object
result from the fraction of diffuse light, and this depends on the type of radiation that
it is used to illuminate the object.
A review and classification of different natural and artificial sources helps in
recognizing a light source as a system able to transform in radiant energy any other
form of energy, as well as to recognize the need to interpret the emission mechanism
(Ph4). This represents a valid context to reinforce the idea that the light emission
process has to be read from an energetic point of view. Sources are analysed in
structural and functional terms, and according to the emitted light. Incandescent,
fluorescence, phosphorescence emissions as well as halogen, gas-discharge lamps,
LED and LASERs are examined (Fig. 19.1) identifying the process of energy
transformation and discussing the different characteristics. Taking into account
different light sources represent a strategy to reinforce the idea that production of
light is an energetic process, in which light is recognized to be an entity carrying
energy, emitted as a consequence of an energetic transformation, rather than a wave
or a particle, which limits the interpretations (Fig. 19.1). The presence of an energetic
exchange between emitting system and emitted light is at the basis of a first
interpretation of the emission processes.
Characteristics of light emitted by different sources are examined and discussed
in terms of colour and intensity (Ph5). Concerning colour, the exploration of the
modalities allowing the production of light of different colours leads to focus on
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D. Buongiorno and M. Michelini
light as a massless entity travelling in space, which possess energy which guides the
description of processes in which light itself interacts with matter causing different
effects, such as heating, penetration, ionization and fluorescence. The difference
between Snell’s law for refraction and the phenomenology of light transmission
through a transparent medium is discussed with students in order to distinguish the
plan of formalized phenomenological description in macroscopic terms and the plan
according to which light–matter interaction processes are interpreted in terms of
energy. A reflection with students on the difference between refraction and transmission of light stimulates an analysis of the two point of view under which those
two apparently similar phenomena, are seen: refraction is a macroscopic phenomenological description of the light path across the interface between two mediums
with different indexes of refraction, while, when speaking of transmission processes,
the focus is put on the interaction between light and matter and implies a deeper
analysis, in particular on the energetic plan.
The problem of what “to see” means is posed to students, with the aim of identify,
from the discussion of spontaneous models, the role of the observer, of the observed
object and of the light (Ph2).
A fundamental parameter enters in the description of the vision mechanism: the
colour (Ph3). Radiation gains a significant role in this perspective and poses the
question of what the colour physically represents, starting from the observation that
what is seen depends on the type of light contextualizing in the case of different
picture or painting appear when illuminated by different lights. Surface absorption
and nano-structuring allows to understand the mechanism according to which
different objects appear differently coloured, in particular the colour of an object
result from the fraction of diffuse light, and this depends on the type of radiation that
it is used to illuminate the object.
A review and classification of different natural and artificial sources helps in
recognizing a light source as a system able to transform in radiant energy any other
form of energy, as well as to recognize the need to interpret the emission mechanism
(Ph4). This represents a valid context to reinforce the idea that the light emission
process has to be read from an energetic point of view. Sources are analysed in
structural and functional terms, and according to the emitted light. Incandescent,
fluorescence, phosphorescence emissions as well as halogen, gas-discharge lamps,
LED and LASERs are examined (Fig. 19.1) identifying the process of energy
transformation and discussing the different characteristics. Taking into account
different light sources represent a strategy to reinforce the idea that production of
light is an energetic process, in which light is recognized to be an entity carrying
energy, emitted as a consequence of an energetic transformation, rather than a wave
or a particle, which limits the interpretations (Fig. 19.1). The presence of an energetic
exchange between emitting system and emitted light is at the basis of a first
interpretation of the emission processes.
Characteristics of light emitted by different sources are examined and discussed
in terms of colour and intensity (Ph5). Concerning colour, the exploration of the
modalities allowing the production of light of different colours leads to focus on
242
D. Buongiorno and M. Michelini